Exercise-associated hyponatremia, renal function, and nonsteroidal antiinflammatory drug use in an ultraendurance mountain run.

OBJECTIVE: To study biochemical parameters and renal function in runners completing a 60 km mountain run and to investigate the incidence of exercise-associated hyponatremia (EAH). To assess the effects of nonselective nonsteroidal antiinflammatory medication (NSAIDs) and cyclooxygenase-2 (COX-2) selective nonsteroidal antiinflammatory medication (COXIBs) on these parameters. DESIGN: Observational cohort study. SETTING: Kepler Challenge 60 km mountain run, Te Anau, New Zealand, December 2003. PARTICIPANTS: One hundred thirty-one of the 360 runners entered in the race were prospectively enrolled as volunteers on the day before the race. MAIN OUTCOME MEASURES: Subjects were weighed at race registration the day before the race and at the finish line. Blood was taken within 5 minutes of finishing and was analyzed for serum sodium, creatinine, urea, and potassium concentrations, and hematocrit. Participants were questioned about medication use in the 24 hours before and during the race (NSAIDs, COXIBs, other medications). RESULTS: Complete data sets were obtained on 123 runners. Five athletes were biochemically hyponatremic [(Na) 130-134 mM] and four were hypernatremic [(Na) 146-148 mM]. Hyponatremia was associated with a mean weight gain of 1.32 kg (range, -1.5 to 1.6 kg). Serum [Na] varied inversely with weight change. Estimated creatinine clearance did not vary with percent weight loss. Estimated creatinine clearance declined with increasing runner age. Sixty-five percent of runners did not use any medication, whereas 20% had used NSAIDs and 15% had taken COXIBs. There were no statistically significant differences between NSAID and COXIB users in any measured parameters or between all NSAID and COXIB users when compared with nonusers. CONCLUSIONS: Mild asymptomatic EAH was found to occur in 4% of the volunteer ultraendurance mountain runner study group and was associated with a mean weight gain of 1.32 kg (range, -1.5 to 1.6 kg) during the race. Seven percent gained weight but remained normonatremic, suggesting other compensatory mechanisms. Hypernatremia was found in 3% and was associated with a mean weight loss. Postrace serum sodium concentration varied inversely with percent weight change. Runners using any NSAID were more likely to become hyponatremic. Estimated creatinine clearance increased with increasing age. Elevated serum creatinine concentration at the end of the race returned to normal when remeasured the week after the race. Thirty-five percent of runners were found to use NSAIDs or COXIBs. The measures of weight change and of serum sodium, potassium, urea, and creatine concentration did not differ between NSAID and COXIB users or between all nonsteroidal antiinflammatory users and nonusers.

Epidemiology of injuries and illnesses in America's Cup yacht racing.

OBJECTIVES: To determine the incidence and severity of injuries and illnesses incurred by a professional America's Cup yacht racing crew during the preparation for and participation in the challenge for the 2003 America's Cup. METHODS: A prospective study design was used over 74 weeks of sailing and training. All injuries and illnesses sustained by the 35 professional male crew members requiring medical treatment were recorded, including the diagnosis, nature, location, and mechanism of injury. The volume of sailing and training were recorded, and the severity of incidents were determined by the number of days absent from both sailing and training. RESULTS: In total, 220 injuries and 119 illnesses were recorded, with an overall incidence of 8.8 incidents/1000 sailing and training hours (injuries, 5.7; illnesses, 3.1). The upper limb was the most commonly injured body segment (40%), followed by the spine and neck (30%). The most common injuries were joint/ligament sprains (27%) and tendinopathies (20%). The incidence of injury was significantly higher in training (8.6) than sailing (2.2). The most common activity or mechanism of injury was non-specific overuse (24%), followed by impact with boat hardware (15%) and weight training (13%). "Grinders" had the highest overall injury incidence (7.7), and "bowmen" had the highest incidence of sailing injuries (3.2). Most of the illnesses were upper respiratory tract infections (40%). CONCLUSIONS: The data from this study suggest that America's Cup crew members are at a similar risk of injury to athletes in other non-collision team sports. Prudent allocation of preventive and therapeutic resources, such as comprehensive health and medical care, well designed conditioning and nutritional programmes, and appropriate management of recovery should be adopted by America's Cup teams in order to reduce the risk of injury and illness.

Response to a fluid load in athletes with a history of exercise induced hyponatremia.

PURPOSE: To determine whether athletes who had previously developed hyponatremia during an ultradistance triathlon show an impaired ability to excrete a large fluid load compared with athletes who had completed the same race without developing hyponatremia. METHODS: Six athletes who had developed hyponatremia ([Na] < 135 mmol x L(-1)) in the 1997 Ironman Triathlon (study cases) were compared with six athletes who completed the same race without hyponatremia (controls). All participants consumed 3.4 L of water over 2 h at rest. Weight, urine output, urine electrolytes, serum [Na(+)], hemoglobin, and hematocrit were measured every 30 min. Changes in plasma volume and residual fluid volume in the gut were estimated from these data. RESULTS: There were no significant differences between cases and controls in any parameters measured. Maximal rates of urine production (+/- SD) (1043 +/- 331 mL x h(-1) for cases, 878 +/- 168 mL x h(-1) for controls) were substantially behind the rate of fluid intake (1500 mL x h(-1)). Consequent to fluid retention, serum [Na(+)] fell progressively in both groups. Five cases and four controls developed hyponatremia. There was an inverse correlation between change in body weight and change in [Na(+)] (r = -0.67). Estimated changes in the intra- and extra-cellular fluid volumes could account for all the retained fluid, and there was little evidence for fluid accumulation in the bowel. CONCLUSION: When evaluated at rest, there does not appear to be any unique pathophysiological characteristic that explains why some athletes develop hyponatremia in response to fluid overload during prolonged exercise. Rather, hyponatremia was induced with equal effect in both cases and controls, consequent to progressive fluid overload of all the body fluid compartments and without evidence for fluid retention in the small bowel.

Exercise-associated hyponatremia: a review.

This paper reviews the extensive literature on hyponatremia, a common and potentially serious complication of ultra-distance exercise. Fluid overload is the likely aetiology. Fluid intakes are typically high in athletes who develop hyponatremia, although hyponatremia can occur with relatively modest fluid intakes. The development of fluid overload and hyponatremia in the presence of a modest fluid intake raises the possibility that athletes with this condition may have an impaired renal capacity to excrete a fluid load. The bulk of evidence favours fluid retention in the extracellular space (dilutional hyponatremia) rather than fluid remaining unabsorbed in the intestine. Female gender is an important risk factor for the development of hyponatremia. Management and prevention of exercise-associated hyponatremia are discussed.

Fluid balance during and after an ironman triathlon.

OBJECTIVE: To record weight changes, fluid intake and changes in serum sodium concentration in ultradistance triathletes. DESIGN: Descriptive research. SETTING: Ironman triathlon (3.8 km swim, 180 km cycle, 42.2 km run). Air temperature at 1200 h was 21 degrees C, (relative humidity 91%). Water temperature was 20.7 degrees C. PARTICIPANTS: 18 triathletes. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Subjects were weighed and had blood drawn for serum sodium concentration [Na], hemoglobin, and hematocrit, pre-race, post-race, and at 0800 h on the morning following the race ("recovery"); subjects were also weighed at transitions. Fluid intake during the race was estimated by athlete recall. RESULTS: Median weight change during the race = -2.5 kg (p < 0.0006). Subjects lost weight during recovery (median = -1.0 kg) (p < 0.03). Median hourly fluid intake = 716 ml/h (range 421-970). Fluid intakes were higher on the bike than on the run (median 889 versus 632 ml/h, p = 0.03). Median calculated fluid losses cycling were 808 ml/h and running were 1,021 ml/h. No significant difference existed between pre-race and post-race [Na] (median 140 versus 138 mmol/L) or between post-race and recovery [Na] (median 138 versus 137 mmol/L). Plasma volume increased during the race, median + 10.8% (p = 0.0005). There was an inverse relationship between change in [Na] pre-race to post-race and relative weight change (r = -0.68, p = 0.0029). Five subjects developed hyponatremia ([Na] 128-133 mmol/L). CONCLUSIONS: Athletes lose 2.5 kg of weight during an ultradistance triathlon. most likely from sources other than fluid loss. Fluid intakes during this event are more modest than that recommended for shorter duration exercise. Plasma volume increases during the ultradistance triathlon. Subjects who developed hyponatremia had evidence of fluid overload despite modest fluid intakes.

Exercise-induced hyponatremia in ultradistance triathletes is caused by inappropriate fluid retention.

OBJECTIVE: To study fluid and sodium balance during overnight recovery following an ultradistance triathlon in hyponatremic athletes compared with normonatremic controls. CASE CONTROL STUDY: Prospective descriptive study. SETTING: 1997 New Zealand Ironman Triathlon (3.8 Km swim, 180 Km cycle, 42.2 Km run). PARTICIPANTS: Seven athletes ("subjects") hospitalized with hyponatremia (median sodium [Na] = 128 mmol L(-1)). Data were compared with measurements from 11 normonatremic race finishers ("controls") (median sodium = 141 mmol L(-1)). INTERVENTIONS: None. MAIN OUTCOME MEASURES: Athletes were weighed prior to, immediately after, and on the morning after, the race. Blood was drawn for sodium, hemoglobin, and hematocrit immediately after the race and the following morning. Plasma concentrations of arginine-vasopressin (AVP) were also measured post race. RESULTS: Subjects were significantly smaller than controls (62.5 vs. 72.0 Kg) and lost less weight during the race than controls (median -0.5% vs. -3.9%, p = 0.002) but more weight than controls during recovery (-4.4% vs. -0.8%, p 0.002). Subjects excreted a median fluid excess during recovery (1,346 ml): controls had a median fluid deficit (521 ml) (p = 0.009). Estimated median sodium deficit was the same in subjects and controls (88 vs. 38 mmol L(-1), p = 0.25). Median AVP was significantly lower in subjects than in controls. Plasma volume fell during recovery in subjects (-5.9%, p = 0.016) but rose in controls (0.76%, p = NS). CONCLUSIONS: Triathletes with symptomatic hyponatremia following very prolonged exercise have abnormal fluid retention including an increased extracellular volume, but without evidence for large sodium losses. Such fluid retention is not associated with elevated plasma AVP concentrations.

A prospective study of exercise-associated hyponatremia in two ultradistance triathletes.

OBJECTIVE: To study fluid and sodium balance in two ultradistance triathletes. DESIGN: Prospective case study. SETTING: An ultradistance triathlon (3.8 km swim, 180 km cycle, 42.2 km run), and during overnight recovery. Ambient air temperature at 12:00 p.m. race day was 21 degrees C, with a relative humidity of 91%. Water temperature was 20.7 degrees C. SUBJECTS: Two female ultradistance triathletes, ages 30 and 39 years, who were participating in a larger study investigating weight and electrolyte changes in the Ironman triathlon. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Subjects were weighed and had blood drawn for serum sodium concentration, hemoglobin, hematocrit, arginine vasopressin, and aldosterone concentration prior to and after the race, and at 8:00 a.m. the following morning. Sodium and fluid intake and urinary output were measured during recovery. RESULTS: Both subjects developed mild hyponatremia (Na 131 and 130 mmol/L) during the race, with a weight gain (0.5 and 1.5 kg). Neither subject had large sodium losses (24 mmol and 20 mmol). Fluid consumption was 733 ml/h and 764 ml/h. Plasma volume increased during the race (25 and 16%). Arginine vasopressin (AVP) levels were not elevated in either subject (1.2 and 1.9 pmol/L). Both subjects demonstrated a water excess during the race (1.5 and 2.5 L), and lost weight during recovery (2.0 and 4.5 kg). CONCLUSIONS: Hyponatremia resulted from fluid retention in the extracellular space, without evidence of large sodium losses or inappropriate AVP secretion.

Diagnosis and prevention of hyponatremia at an ultradistance triathlon.

OBJECTIVE: To evaluate a method of medical care at an ultradistance triathlon, with the aim of reducing the incidence of hyponatremia. DESIGN: Descriptive research. SETTING: New Zealand Ironman triathlon (3.8 km swim, 180 km cycle, 42.2 km run). PARTICIPANTS: 117 of 134 athletes seeking medical care after the triathlon (involving 650 race starters). INTERVENTIONS: A prerace education program on appropriate fluid intake was undertaken. The number of support stations was decreased to reduce the availability of fluid. A body weight measurement before the race was introduced as a compulsory requirement, so that weight change during the race could be included in the triage assessment. An on-site laboratory was established within the race medical tent. MAIN OUTCOME MEASURES: Numbers of athletes and diagnoses, including the incidence of symptomatic hyponatremia (defined as symptoms of hyponatremia in association with a pretreatment plasma sodium concentration [Na] < 135 mmol/L); weight changes; and changes in [Na]. RESULTS: The common diagnoses in the 117 athletes receiving attention were exercise-associated collapse (27%), musculoskeletal complaints (26%), and dehydration (12%). There was a significant reduction in the number of athletes receiving medical care for hyponatremia, from 25 of the 114 athletes who received care in 1997 (3.8% of race starters) to 4 of the 117 athletes who received care in 1998 (0.6% of race starters). Mean weight change among athletes in the 1998 race was -3.1 kg, compared with -2.6 kg in 1997. CONCLUSION: A preventive strategy to decrease the incidence of hyponatremia, including education on fluid intake and appropriate placement of support stations, was associated with a decrease in the incidence of symptomatic hyponatremia.

Hyponatremia and seizures in an ultradistance triathlete.

Hyponatremia is being increasingly recognized as a complication of participation in ultra-endurance sports. Reported is the case of an Ironman triathlete who collapsed at the end of the race, having gained 5% in body weight. His serum sodium concentration at the finish was 116 mmol/L. After an Intensive Care Unit course complicated by recurrent seizures, he eventually made a complete neurologic recovery. The pathogenesis of hyponatremia and its management in such cases is discussed.

Hyponatremia in ultradistance triathletes.

PURPOSE: Hyponatremia ([plasma sodium] <135 mmol x L(-1)) is a potentially serious complication of ultraendurance sports. However, the etiology of this condition is still uncertain. This observational cohort study aimed to determine prospectively the incidence and etiology of hyponatremia in an ultradistance triathlon. METHODS: The subjects consisted of 605 of the 660 athletes entered in the New Zealand Ironman triathlon (3.8-km swim, 180-km cycle, and 42.2-km run). Subjects were weighed before and after the race. A blood sample was drawn for measurement of plasma sodium concentration after the race. RESULTS: Complete data on pre- and postrace weights and plasma sodium concentrations were available in 330 race finishers. Postrace plasma sodium concentrations were inversely related to changes in body weight (P = 0.0001). Women (N = 38) had significantly lower plasma sodium concentrations (133.7 vs 137.4 mmol x L(-1); P = 0.0001) than men (N = 292) and lost significantly less relative weight (-2.7 vs -4.3%; P = 0.0002). Fifty-eight of 330 race finishers (18%) were hyponatremic; of these only 18 (31%) sought medical care for the symptoms of hyponatremia (symptomatic). Eleven of the 58 hyponatremic athletes had severe hyponatremia ([plasma sodium] < 130 mmol x L(-1)); seven of these 11 severely hyponatremic athletes were symptomatic. The relative body weight change of the 11 severely hyponatremic athletes ranged from 2.4% to +5%; eight (73%) of these athletes either maintained or gained weight during the race. In contrast, relative body weight changes in the 47 athletes with mild hyponatremia ([plasma sodium] 130-134 mmol x L(1)) were more variable, ranging from -9.25% to +2.2%. CONCLUSIONS: Hyponatremia is a common biochemical finding in ultradistance triathletes but is usually asymptomatic. Although mild hyponatremia was associated with variable body weight changes, fluid overload was the cause of most (73%) cases of severe, symptomatic hyponatremia.

Hyponatremia and weight changes in an ultradistance triathlon.

OBJECTIVE: To describe the weight changes and the incidence of hyponatremia during an ultradistance triathlon in the athletes who attend medical care after the race. DESIGN: Descriptive research. SETTING: The 1996 New Zealand Ironman Triathlon in which each athlete swam 3.8 km, cycled 180 km, and ran 42 km. PARTICIPANTS: Ninety-five athletes attending for medical care after the race were studied. One hundred sixty-nine athletes who did not attend for medical care were also weighed before and after the race. MAIN OUTCOME MEASURES: Weights were measured at race registration and on finishing the race. Whole-blood sodium concentration was measured in those athletes with clinical evidence of fluid or electrolyte disturbances. RESULTS: Weights were significantly decreased at the end of the race in the athletes seeking medical care (n = 48, mean % delta wt = -2.5%, p < 0.001) and also in the athletes who did not seek medical care (n = 169, mean % delta wt = -2.9%, p < 0.001). Seventeen percent of race starters sought medical attention. Dehydration accounted for 26% of primary diagnoses and hyponatremia for 9%. One athlete with hyponatremia (Na 130 mEq/L) is described who drank 16 L over the course of the race, with a weight gain of 2.5 kg. This is consistent with the hypothesis of fluid overload as the cause of his hyponatremia. Hyponatremia accounted for four of five admissions to the hospital after the race. An inverse relationship between postrace sodium concentrations and percentage change in body weight was observed (r = -0.63). CONCLUSIONS: Hyponatremia is an important risk to the health of athletes competing in an ultradistance triathlon, with fluid overload the likely aetiology.

Weight changes and serum sodium concentrations after an ultradistance multisport triathlon.

OBJECTIVE: This study describes the incidence of hyponatremia and the weight changes during an ultradistance multisport triathlon. DESIGN: Descriptive research. SETTING: A 1-day triathlon in which each athlete kayaks 67 km, cycles 148 km, and runs 23.8 km. PARTICIPANTS: Forty-eight athletes competing in the race were studied. INTERVENTIONS: None. MAIN OUTCOME MEASURES: All subjects were weighed before the race and on completion of the race. A blood sample for serum sodium was taken at the finish of the race. RESULTS: The mean weight change over the course of the race was a loss of 2.5 kg (SD +/- 1.7, n = 48), or a mean percentage loss of body weight of 3.1% (SD +/- 2.07). This was highly statistically significant (p < 0.0001) using the Student paired t test. No athletes gained weight, and six athletes maintained their same weight. Only one athlete was hyponatremic (Na = 134 mEq/L). This athlete maintained his weight over the course of the race and he did not seek medical attention. The mean serum sodium concentration at the end of the race was 139.3 mEq/L (SD = 2.28, n = 47). There was a significant correlation (r = 0.30, p = 0.04) between sodium levels and weight change during the race: the greater the weight loss, the higher the serum sodium concentration. There was no significant correlation between the degree of weight loss and athletes' finishing times (r = 0.11, p = 0.45). CONCLUSIONS: Symptomatic hyponatremia did not occur in the 1996 Coast to Coast multisport triathlon, although one athlete had borderline hyponatremia. Athletes lose significant amounts of weight over the course of this multisport event, but nevertheless manage to complete the race.